Macroevolution

Describes patterns of evolution for groups of species over extended periods of geologic time.

Mesozoic Era

An era of time lasting from 245 million to 65 million years ago in the earth's history. This era is marked by the emergence and extinction of the dinosaurs.

Metazoa

Term applied to all multicellular organisms that digest food, including sponges and higher animals.

Meiosis

The process of division in some cells of the sex organs that reduces the number of chromosomes to half the number found in somatic cells.

Microbiology

The study of microscopic organisms, scientifically known as microorganisms.

Microevolution

Describes the details of how individual populations and species evolve and how new species originate.

Microorganism

Another term for microscopic organism. These include algae, bacteria, molds, protozoans, viruses, and yeasts.

Miocene

An epoch of time lasting from 26 million to 7 million years ago in the earth's history.

Mitosis

The process of cell division in which two identical daughter cells are produced, with each containing the full number of chromosomes.

Mold

A tiny, simple plant which belongs to the fungi group.

Molecular Biology

The study of those molecules that direct molecular processes in cells.

Molecule

One of the basic units of matter. It is the smallest particle into which a substance can be divided and still have the chemical properties of the original substance.

Morphological Isolation

Prezygotic isolating mechanism that occurs when differences in shape or size prevent mating between species.

Morphology

The biological study of the form and structure of living organisms.

Mutation

A chemical change in a gene. It may produce a new trait that can be inherited.

Mutation Rate

Frequency with which a particular mutation occurs.

Mutationism

A theory of evolution that plays greater emphasis on the role of mutation in evolution.